The Paraffin Method 117 



Clove oil is also an excellent clearing agent. The clove oil should 

 follow the absolute alcohol, without any mixtures. Pour on a few 

 drops of clove oil, and drain them off at once in such a way as to carry 

 with them whatever alcohol may still remain. Then flood the slide 

 repeatedly with clove oil, draining the clove oil back into the bottle. 

 If judiciously used, 50 c.c. of clove oil is enough to clear one hundred 

 preparations. Sections are usually cleared in a few seconds. The 

 only objection to clove oil is that mounts harden slowly. To over- 

 come this difficulty, the slide may be dipped in xylol before mounting 

 in balsam. 



For clearing sections on the slide, other clearing agents are 

 hardly worth mentioning. 



MOUNTING IN BALSAM 



After the sections are cleared, wipe the slide on the side which 

 does not bear the sections. Put 011 a drop of Canada balsam and 

 add a clean, 1 thin cover. Before the cover is put on, pass it through 

 the flame of an alcohol lamp to remove moisture, for it would be a pity 

 indeed to injure a preparation at this stage of the process. Add a 

 label, and the mount is complete. 



A TENTATIVE SCHEDULE FOR PARAFFIN SECTIONS 



It will be useful to give several tentative schedules for the use 

 of beginners. It cannot be too strenuously insisted that these 

 schedules are only tentative, their sole object being to give the beginner 

 a start. The following is a tentative schedule for the ovary of a lily 

 at any period before fertilization. The pieces should not be more 

 than 12mm. in length. 



1. Chromo-acetic acid, 1 day. 



2. Wash in water, 1 day. 



3. 2|, 5, 7^, 10, 15, 20, 30, and 50 per cent alcohol, 4 hours each; 70, 

 85, and 95 per cent alcohol, 10 hours each; absolute alcohol, 12 to 

 24 hours, changing two or three times. 



1 Slides and covers should be treated with hydrochloric acid, or equal parts of hydro- 

 chloric acid and water, for several hours. They should then be thoroughly rinsed in 

 water and wiped with a cloth perfectly free from lint. After rinsing in water, they may be 

 kept in 95 per cent alcohol. When a cover is needed for use, it is Dr. Land's practice to 

 rest the corner of the cover on a piece of filter paper to remove the drop of alcohol ; then 

 pass the cover through the flame of a Bunsen or alcohol lamp. The film of alcohol will 

 burn and the cover may warp, but it will usually straighten, and it will be clean and dry. 



